The invention relates to a driving device for a rollover bar.
DE 39 25 513 C2 describes a driving device for a rollover bar of a motor vehicle, in particular a convertible. By means of this driving device, the rollover bar can be displaced out of its lowered rest position into an upward-pointing supporting position and back again. For this purpose, the rollover bar is connected to a first actuating element, which can be actuated underneath by the action of a spring energy store and is controlled by a sensor, and a second actuating element, the direction of movement of which can be controlled arbitrarily. The two actuating elements are supported against the vehicle body, on which a retention device for the lowered rollover bar and an interlock device for the rollover bar in a supporting position are provided. The retention device comprises a retaining lever which, in the rest position, projects into the path of movement of the rollover bar and which can be pivoted out of this path. One end of this lever interacts with a corresponding retaining projection on this rollover bar, and the lever is actuated counter to a spring force by an actuating rod of a hydraulic cylinder. The retaining lever is a two-arm lever, one lever arm being assigned to the retaining projection of the rollover bar and the other lever arm being capable of being acted upon by the actuating rod.
However, the disadvantage here is that, if the motor vehicle is involved in a crash or rolls over, the rollover bar has to be released by the retaining lever before being displaced into its upward-pointing supporting position.
Another disadvantage is that it releases the force by means of a hydraulic actuator which operates particularly quickly and can be acted upon by means of an accumulator, actuators of this kind being limited in terms of their response time due to high viscosities of the pressure media employed. Under certain circumstances, extension of the rollover bar due to a crash can therefore be delayed.
Another driving device for a rollover bar for motor vehicles is described in DE 37 32 562 C1. This driving device has a piston-cylinder unit by means of which the rollover bar can be extended out of a lowered rest position into a raised supporting position in a crash situation. After controlled release of an interlock, a supporting piston is extended out of a guide cylinder by means of an ejection spring and interlocked again in the extended position. For the adjustment of the piston-cylinder unit, there is a further piston-cylinder unit as an additional drive, by means of which the direction of movement and speed of the spring-loaded supporting piston can be arbitrarily controlled. The influence of the further piston-cylinder unit on the supporting piston can be cancelled in the presence of a crash signal. A detent toothing which acts counter to a retraction movement of the supporting piston is furthermore formed on the supporting piston, and by means of this detent toothing a controllable detent element can be brought into engagement by means of a hydraulic cylinder in any extended position. A piston of the further piston-cylinder unit is held releasably in its retracted position by a controllable locking device.
However, this locking device has the disadvantage that its design configuration, production and assembly are involved and lead to high costs.
Refinements of a locking device of this kind are described in DE 37 32 561 C 2 and in EP 0 568 858 B1.
The object of the present invention is therefore to provide a driving device for a rollover bar by means of which the rollover bar can be locked in any extended position and by means of which it is possible to immediately raise the rollover bar into its supporting position in the event of an accident, its embodiment being extremely simple and economical.
According to the invention, the locking device is moved in such a way by the hydraulic cylinder, which is furthermore provided to actuate the detent element, that the piston of the further piston-cylinder unit is released during extension of the rollover bar out of its rest position and otherwise is held in the rest position by the locking device. This is done advantageously by way of preventing the piston of the further piston-cylinder unit and the rollover bar from creeping out of the lowered rest position of the rollover bar in the direction of the extended supporting position of the rollover bar in the event of low working pressure in the further piston-cylinder unit, an additional controllable actuating element for actuating the locking device and hence for releasing the piston being superfluous. This reduces the production costs for the driving device according to the invention, the outlay on assembly and the number of components.
In addition to simplified design, the driving device according to the invention has the advantage that the outlay on control and regulation for adjusting the rollover bar is significantly reduced.